Gulf of Maine 2022: Sea Surface Temperature
This report was created to track the sea surface temperature regimes for marine regions of interest to the Gulf of Maine Research Institute. Historically the focus has been on a central snapshot of the Gulf of Maine. A region that has experienced profound temperature increases in recent years.
Satellite sea surface temperature data used was obtained from the National Center for Environmental Information (NCEI). With all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.
DISCLAIMER: Any data within 2-weeks of the current date are subject to revision and may change. Please use caution when reporting information that contains these values.
Gulf of Maine On a Map
Whenever discussing the Gulf of Maine in this report, we refer to the following spatial extent displayed below. The coordinates of this bounding box are the same coordinates used to clip the sea surface temperature data.
1: Temperature History
Using the coordinates shown above we can create an area-specific temperature history. For any day of the year since September of 1981, data is available to calculate the average sea surface temperature within that area for each day.
Additionally, we can compare observed temperatures against the expected conditions based on a climatology using a specified reference period. The standard reference period used for the climatology here is 1982-2011, a 30-year period.
Climatological Patterns of the Gulf of Maine
Daily climatologies are a record of daily averages based on the day of the year. They record what the average temperature has been for each day of the year, across the specified reference period.
In addition to the daily average, we also look at how variable temperatures are. This variability is used to benchmark how “rare” extreme events are to determine whether they are part of a natural cycle or not.
Common benchmarks for extreme events are the 10th and 90th percentile. Temperatures above the 90th percentile are among the hottest 10% of days in the reference period. Temperatures below the 10th percentile correspond to the coldest 10%. The remaining 80% of days fall somewhere in-between and showcase the range of temperatures we might expect to occur given the natural variability of the climate.
Working in Anomalies
Using the climatology as a reference, we can see hot much “hotter” or “colder” a given day is than what we would on average expect. This difference from the average is what we call anomalies.
In the table below, Sea Surface Temperature is the mean
temperature observed for that date averaged across all cells within the
area. Climate Avg. & Climate SD are the
climate means and standard deviations for a 1982-2011 climatology.
Temperature Anomaly is the daily observed sea surface
temperature minus the climate mean.
In this way a Temperature Anomaly is just: How much
hotter or colder is it than the average temperature for that day.
| Gulf of Maine - Regional Sea Surface Temperature | ||||
|---|---|---|---|---|
| Temperature Unit: Celsius | ||||
| Date | Sea Surface Temperature | Day of Year | Climate Avg. | Temperature Anomaly |
| 2022-06-29 | 14.60 | 181 | 13.48 | 1.12 |
| 2022-06-30 | 14.96 | 182 | 13.62 | 1.34 |
| 2022-07-01 | 15.16 | 183 | 13.68 | 1.48 |
| 2022-07-02 | 16.22 | 184 | 13.81 | 2.40 |
| 2022-07-03 | 16.39 | 185 | 13.96 | 2.43 |
| 2022-07-04 | 16.26 | 186 | 14.11 | 2.15 |
| Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data. | ||||
| Climatology Reference Period: 1982-2011. | ||||
Detecting Long-Term Changes
One reason we go through this trouble of calculating climatologies and anomalies is to set expectations around how much we expect things to naturally vary, and to detect when things fall outside that range.
In the case of the Gulf of Maine we are now consistently outside of the range of temperatures normally expected from 1982-2011. The following plot colors the monthly average by how far temperatures are from the climatological average. Blue colors represent a month that was cooler than average, with red indicating a warmer than average month.
Warming Rates
Seeing this change towards a warmer climate, it is then natural to ask how rapidly the change is happening. This is where we turn to warming rates. The warming trends below were calculated using all the available data for complete years beginning with 1982 through the end of 2021.
The overlaid trend lines then track how warming has increased with time. A dotted line has been included to show how the global average temperature has changed during the same period.
Warming Trends
Shift in Regional Ocean Circulation
Beginning around 2008, temperature in the region swung upward, and since 2010 most yearly temperatures have been over 1 degree above the hematological average of the previous 30-years. With some years experiencing temperatures more than 2 degrees C above that average.
The magnitude of this regime shift was 1.25C, or 2.25F. Bringing average yearly temperatures up from the 30-year average of 9.98C to 11.24C, or 49.97F to 52.22F.
Seasonal Patterns
Overall Temperature Increase
Marine Heatwaves
A marine heatwave is defined as a situation when seawater temperatures exceeds a seasonally-varying threshold (usually the 90th percentile) for at least 5 consecutive days. Successive heatwaves with gaps of 2 days or less are considered part of the same event. The heatwave threshold used below was 90%. The heatwave history for Gulf of Maine is displayed below:
Note: For the figures below heatwave events were determined using the methods of Hobday et al. 2016 and implemented using the R package {heatwaveR}.
Heatwave Events
Heatwave Trends
2: 2022 Observations
Last Full Year (Interactive)
Daily temperatures for the last 365 days are displayed below with reference to how they fall against the marine heatwave and cold spell thresholds.
2022 Temperatures
Temperatures for the current year can be seen against the same thresholds with the following plot:
2022 Anomalies
Changing from absolute temperatures to anomalies reveals the degree to which this year is departure from what we would have expected from the climatology of 1982-2011’s temperatures.
2022 in Context
When 2022 is overlaid against the daily values and climatological average for the region, we can see how temperatures compare to the history of the region.
3: Global Temperature Maps
The 2021 global sea surface temperature anomalies have been loaded and displayed below to visualize how different areas of the ocean experience swings in temperature.
For perspective on where excess heat is distributed around the world, here first are maps of anomalies at a global perspective:
Annual Average
Winter
Spring
Summer
Fall
4: Regional Temperature Maps
The regional views of 2021’s sea surface temperature anomalies have been loaded and displayed below to visualize how localized differences changed throughout the year.
Annual Average
Winter
Spring
Summer
Fall
Heatwave Progression
Looking specifically at the last heatwave event, we can step through how the event progressed over time, and developing pockets or warmer/colder water masses.
5: Ranking Warming Rates
If we look at the rates of change from 1982-2021 for each grid cell, rather than the observed temperature, it is possible to rank how hot each location on earth is warming relative to all the others.
Once we have the rankings, we can then take the average ranking within the Gulf of Maine we can obtain the average warming rank for the area compared to the rest of the globe.
Based on data from 1982-2021, the warming rates of Gulf of Maine have been some of the highest in the world. The area as a whole has been increasing at a rate of 0.044\(^{\circ}C/year\) which is faster than 95.9% of the world’s oceans.
Over that same period locations within the Gulf of Maine have been warming at rates as low as 0.017\(^{\circ}C/year\) and as rapidly as 0.094\(^{\circ}C/year\), corresponding to ranks as low as 60.3% and as high as greater than or equal to 99.5%.
Mapped below are the corresponding warming rates and their global rankings.
Warming Rates
Warming Ranks
6: Shifting Baselines
In 2021 NOAA is transitioning standard climatologies from the 30-year period of 1982-2011 to a new period spanning 1992-2020. Changes in climate regimes often does not result in a uniform upward or downward change that is consistent throughout the year.
The plot below shows just how both the average temperature, as well as the annual highs and lows have shifted. When looking specifically at Gulf of Maine here is how the expected temperature for each day of the year has shifted.
From this we can see that the Fall temperatures have risen more than those of the spring. There is also a large change in where the threshold for Marine Heatwave events sits, a consequence of exceptionally warm Fall temperatures becoming more common.
A work by Adam A. Kemberling
Akemberling@gmri.org